1. Field of the Invention
The invention relates to a detector of embedded elongate objects, particularly of plastic tubular conduits embedded in masonry, and to an associated measurement method.
2. Description of the Prior Art
The detection of embedded elongate objects, i.e., objects extending substantially along one dimension, plays an important role in the constructional industry for detecting iron reinforcements, metal pipes, electric lines or plastic conduit. Embedded elongate objects are detected and identified by the change in impedance of an impressed magnetic near-field, e.g., according to U.S. Pat. No. 6,541,965, by the change in impedance of an impressed electric near-field according to DE 102 39 432, or electromagnetically by a radar according to U.S. Pat. No. 5,541,605. Since the two last-mentioned measurement principles respond physically particularly to the change in the dielectric constant, detection of the plastic tubular conduits in masonry, which have a dielectric permittivity of about 4 to 8 or approximately 4.3 in the frequency range of 1-10 GHz, presents a challenge with respect to the measurement technique. Detection of plastic tubular conduit in masonry is made more difficult by the cavities which are introduced in masonry for thermal insulation in bricks because their dimensions and position are similar to those of plastic tubular conduits.
U.S. Pat. No. 5,296,807 discloses a handheld detector for embedded elongate objects and has a handheld measuring head that can be moved over the surface for measuring an impressed magnetic near-field, a path detector, and a spatially separate, image-generating evaluating unit having a signal-transmitting connection to the measuring head.
Further, according to U.S. Pat. No. 6,600,441, in a radar detector for embedded elongate objects, several pairs of antenna are provided at a predetermined distance from one another. A signal processor selects elongate objects from the separate radar measurement signals of the antennae using correlation functions, and determines their length in the plane. Further, a radar detector with a patch antenna is disclosed in Publication WO 02063334.
In addition, modern methods of computer-assisted signal processing particularly of time-based 3D measurement data, which are not, per se, the subject of the present invention, are known to a person skilled in the art.